Page 93 - Mobile Computing

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 As nodes move, the connectivity may change based on relative locations

of other nodes. The resulting change in the network topology known at the
local level must be passed on to other nodes so that old topology
information can be updated.
 For example, as MS2 in the figure changes its point of attachment from
MS3 to MS4, other nodes that are part of the network should use this new
route to forward packets to MS2. In the figure, we assume that it is not

possible to have all nodes within each other's radio range. In case all nodes
are closed by within each other's radio range, there are no routing issues to
be addressed.
 In figures raise another issue, that of symmetric and asymmetric
(bidirectional) and asymmetric (unidirectional) links. Consider symmetric

links with associative radio range; for example, if MS1 is within radio
range of MS3, then MS3 is also within radio range of MS1. The
communication links are symmetric. This assumption is not always valid
because of differences in transmitting power levels and the terrain. Routing
in asymmetric networks is relatively hard task. In certain cases, it is
possible to find routes that exclude asymmetric links, since it is

cumbersome to find the return path. The issue of efficient is one of the
several challenges encountered in a MANET.
 The other issue is varying the mobility patterns of different nodes. Some
other nodes are highly mobile, while others are primarily stationary. It is
difficult to predict a node's movement and direction of movement and

numerous studies have been performed to evaluate their performance using
different simulators.

Advantages of MANET

The advantages of an Ad-Hoc network include the following:

 They provide access to information and services regardless of geographic

position.
 Independence from central network administration. Self-configuring
network, nodes are also act as routers. Less expensive as compared to wired
network.

 Scalable—accommodates the addition of more nodes.
 Improved Flexibility.
 Robust due to decentralize administration.
 The network can be set up at any place and time